Conventionally, as an illumination light source used for illuminating goods displayed in a display case such as a showcase, a fluorescent light is used (see, for example, JPn. Pat. Appln. KOKAI Publication No. 2003-16830). The illumination light source in the patent application illuminates various kinds of goods displayed in, for example, a showcase, and has an important role for showing a commercial value of the product. In addition, the fluorescent light is used for not only the showcase but also, for example, general lighting (for example, room light and desk light), advertisement lighting, wall lighting, and a sidewalk light as the illumination light source.
On the other hand, recently, as a lighting unit to replace the fluorescent light, a line-shaped lighting unit using a semiconductor light emitting device such as a light emitting diode as a light source has been proposed. For example, the lighting unit which is provided with a plurality of LEDs (light emitting device) mounted along the longitudinal direction of a board and a transmissive resin portion having substantially a half-columnar shape, or a hog-backed shape has been proposed (see, for example, JPn. Pat. Appln. KOKAI Publication No. 2002-299697).
In addition, another lighting unit has been proposed (see, for example, claim 1 and FIG. 2 in JPn. Pat. Appln. KOKAI Publication No. 2005-108544), in which a board that arranges LEDs on the front surface and has wiring patterns for the LEDs on the front and back surfaces and a through-hole surrounded by the LEDs, is housed in a basket with a bottom so that the LEDs array is arranged in parallel with an opening face of the basket and a clearance is formed between an inner surface of the basket and the board, and the basket is exhausted from the bottom of the basket. In the lighting unit which integrally arranges a plurality of LEDs as described above, a temperature of the board on which the LEDs are arranged is raised due to the light emission of the LEDs. Therefore, a means for suppressing the temperature rise of the board is required. In the lighting unit which is disclosed in JPn. Pat. Appln. KOKAI Publication No. 2005-108544, the temperature rise of the board when the LEDs emit light is suppressed by air passing through the through-hole disposed on the board and air passing through the clearance between the inner surface of the basket and the board.
The semiconductor light emitting device such as the light emitting diode has many following advantages. The lifetime is long in comparison with a fluorescent light. The power consumption is low due to high energy efficiency. The handling is easy and robust because of a solid state device. An environmentally hazardous material, such as mercury is not contained. The optical control is easy since the light can be assumed as a point source which emits the light only to the front side (hemisphere) of the LED, thereby a light usage efficiency can be increased when the LED is used as a lamp. Accordingly, in the lighting unit using a semiconductor light emitting device as a light source, a maintenance cost and a running cost can be reduced due to, for example, a long time between the replacements of the light source and easiness of handling.
In addition, as a method for holding a conventional lighting unit at an arbitrary angle, the method which has a locking member to be fixed to a bracket and a fastening member to which the lighting unit is fixed has been proposed (see, for example, claim 1 and FIG. 5 in JPn. Pat. Appln. KOKAI Publication No. 2005-116197), in which the lighting unit is fixed by winding up the fastening member around the locking member to fasten up. In the method for fixing the lighting unit disclosed in the JPn. Pat. Appln. KOKAI Publication No. 2005-116197, more specifically, a cylindrical member is used for the locking member and the locking member is fixed to a frame of, for example, a display case to which the lighting unit is fixed. Therefore, the locking member does not rotate. The fastening member consists of a circular arc curved portion which substantially covers a whole circumferential curved surface of the locking member in the circumferential direction and two plate portions projected from an end of the curved portion. If the two plate portions are fastened each other by a screw, the curved portion fastens up the locking member. Then, the fastening member is fixed to the locking member and the lighting unit fixed to the fastening member is fixed to a predetermined position.